INORGANIC CHEMISTRY

EXERCISE I (A)
Q1. Onadding ammoniumhydroxide solutiontoAl2(SO4)3 (aq):
(A) a precipitateis formed which does not dissolve inexcess ofammoniumhydroxide.
(B)Aprecipitate is formed whichdissolves inexcess ofammonia solution.
(C) No precipitate is formed
(D) None ofthese
Q2. The weakest Lewis acid is
(A) BF3 (B) BCl3 (C) BBr3 (D) BI3
Q3. Whichstatement is correct for B2H6:
(A) 4B–H bonds are ofequallengthand 4B–H bonds are another but equallength
(B) H–B–H angles are 1200 and 970
(C) B–Hbonds length
(D)Allofthese
Q4. Whichofthefollowingreactionwillyield crystallinevarietyofboron:
(A) B2O3 + 2Al  2B + Al2O3 (B) B2O3 + 3Mg  2B + 3MgO
(C) B2O3 + 6Na  2B + 3Na2O (D)Allofthese
Q5. Fluorine is moreelectronegative thaneither boronor phosphorus. What conclusioncanbe drawnfrom
the fact that BF3 has no dipole moment but PF3 does.
(A) BF3 is not sphericalysymmetrical, PF3 is not.
(B) BF3 molecule must be linear
(C) The atomic radius ofP is larger thanthe atomic radius ofB.
(D) The BF3 molecule must be plaanr triangular
Q6. BCl3 does not exist as dimer but BH3 exist as dimer (B2H6) becuase
(A) Chlorine ismore electronegative thanhydrogen
(B) There is p-p back bonding in BCl3 but does not contain suchmultiple bonding
(C)Large sizedchlorineatoms do notfit inbetweenthesmallboronatomswhereassmallsized hydrogen
atoms get fitted betweenboron atoms
(D) noneofthese
Q7. Whichofthefollowing statement about boroncarbide is wrong:
(A) Its molecularformula is B4C (B) It is also called Norbia
(C) It is the hardest substance (D) It isused for cutting glasses
Q8. Select the correct statements for diborane
1. Boron is approximatelysp3 hybridized
2. B–H–B angle is 1800
3. There are two terminalB–H bonds for each boron atom
4. There are only12 bonding electrons available ofthese statements
(A) 1, 2 and 4 (B) 1, 2 and 3 (C) 2, 3 and 4 (D) 1, 3 and 4
Q9. The structureofaluminiumbromide is best represented as:
(A) (B) [AlBr2]+ [AlBr4]–

(C) (D)
Q10. Whichone ofthe following methyldiboranes does not exist?
(A) B2H4(CH3)2 (B) B2H3(CH3)3 (C) B2H2(CH3)4 (D) B2H(CH3)5
Q11. Boraxonheatingstronglyabove its melting point melts to aliquid, thensolidifies to a transparent mass
commonlyknown asBoraxBead. The transparent glassymass consists of:
(A) sodiumpyroborate (B) boric anhydride
(C) sodiummetaborate (D) mixtureofsodiummetaborate andboric anhydride
Q12. Me3B, BH3 and BF3 arethree Lewis acids. Whichone ofthe followingis the correct sequenceofthese
acids inorder oftheir increasingacid strength?
(A) Me3B < BH3 < BF3 (B) Me3B < BF3 < BH3
(C) BF3 < Me3B < BH3 (D) BF3 < BH3 < Me3B
Q13. Be andAlexhibit manyproperties whichare similar, but the two elements differ in:
(A) Exhibiting amphotericnature intheiroxides
(B) Formingpolymeric hydrides
(C)Exhibiting maximumcovalencyincompounds
(D) FOrmingcovalent halides
Q14. Aluminiumchloride existsas dimer,Al2Cl6 insolid state as wellas insoluitonofnon-polar solvents such
as C6H6. When dissolvedin water it gives:
(A) Al2O3 + 6HCl (B) [Al(H2O)6]+ 3Cl–
(C) [Al(OH)6]3–+ 3HCl (D)Al3+ + 3Cl–
Q15. Heating anaqueoussolutionofaluminiumchloride todryness willgive:
(A)AlCl3 (B)Al2Cl6 (C) Al2O3 (D)Al(OH)Cl2
Q16. The structureofdiborane contains:
(A) Four 2C–2e bonds and two 3C–2e bonds (B) Two 2C–2e bonds and two 3C–2e bonds
(C) Two 2C–2e bonds and two 3C–3e bonds (D) Four 2C–2e bonds and two 3C–3e bonds
Q17. H3BO3 is
(A) Monobasic and weak Lewis acid (B) Monobasic and weak Bronsted acid
(C) Monobasic and strong Lewis acid (D) Tribasic and weak Bronsted acid
EXERCISE I (B)
Q1. Correct matchis:
(A) Ordinaryformofborax : Na2B4O7 · 5H2O
(B) Colemanite : Ca2B6O11·5H2O
(C) Boronatrocalcite : 2Mg3B8O15·MgCl2
(D) Octahedralformofborac : Na2B4O7·10H2O
Q2. Which ofthe following is correct?
(A) The members ofBnHn+6 are less stable than BnHn+4 series
(B) Diboraneis coloured and unstable at roomtemperature
(C) Thereactionofdiborane withoxygen is endothermic
(D)Allofthe above

Q3. In which ofthe following, a salt ofthe type KMO2 is obtained?
(A) B2H6 + KOH (aq)  (B) Al + KOH (aq) 
(C) Both (D) None
Q4. Whichofthe following mineraldoesnot containaluminium?
(A) Cryolite (B) Mica
(C) Feldspar (D) Fluorspar
Q5. The functionoffluorsparinthe electrolyticreductionofalumina dissolvedinfused cryolite(Na3AlF6)is:
(A) as a catalyst
(B) to lowerthe temperature ofmelt and to make the fused mixture veryconducting
(C) to decrease the rate ofoxidationofcarbon anode
(D) none of the above
Q6. Alayerofcoke is spreadover bauxite during electrolyticreductionofalumina byHall–Heroult process.
This layeracts as a/an:
(A)flux (B) slagto remove impurities
(C) reducing agent (D) insulationand does not allow heat to escape
Q7. Which ofthe following compound is formed inborax bead test?
(A) Metaborate (B) Tetraborate
(C) Double oxide (D) Orthoborate
Q8. Aluminiumchloride exists as a dimer,Al2Cl6, insolid state as wellas in solution ofnon-polar solvents
suchasbenzene.When dissolved in water, it gives:
(A)Al3+ +3Cl– (B) [Al(H2)6]3+ + 3Cl–
(C) [Al(OH)6]3– + 3HCl (D)Al2O3 + 6HCl
Q9. Inorganic graphite is:
(A) B3N3H6 (B) B3N3 (C) SiC (D) P4S3
Q10. HydratedAlCl3 is used as:
(A) catalysed incracking ofpetroleum (B) catalysed inFriedel–Craft's reaction
(C) Mordant (D) allofthe above
EXERCISE II (A)
Q1. IdentifyA, B and C in the given reaction sequence.
NH4Cl + BCl3 C
150
140
Cl
H
C
0
5
6



 
 A MgBr
CH
NaBH
3
4


 
 B
Q2. Identifythe productAand B in thegivenreactionsequence.
A + CO 

 
diglyme B 
 
 2
2O
H [CH3·CH2]3 – C – OH
Q3. An inorganiccompound (A) shows thefollowing reactions. It iswhite solid and exist as dimer.
(i) It givesfumes of(B) withmuch wet air.
(ii) It sublimes on 1800C and forms monomer ifheated to 4000C.
(iii) Itsaqueous solutionturns bluelitmus to red.
(iv)Addition of NH4OH and NaOH separately to a solution of (A) gives white precipitate which is
however soluble inexcess ofNaOH.

Q4. Aninogranic compound (A) in itsaqueous solutionproduced a white ppt. with NaOH, whichdissolves
inexcess ofNaOH. The aqueous solutionof(A) also produced whiteppt. withNH4OH whichdoes not
dissolveinexcess ofNH4OH.Also itsaqueous solutionproduced light yellowppt. withAgNO3 solution,
soluble in dil. HNO3. Identify(A).
Q5. A white crystalline compound (A) swells up on heating and gives violet colour flame on burning. It's
aqueoussolutiongives:
(A) White ppt. with BaCl2
(B) White gelatinous ppt. with excess ofNH4OH which dissolves in NaOH but reappears on boiling
withconc. NH4Clsolution. Identifythe compound(A) andgive the reactions.
Q6. Complete thefollowing reaction:



 

OH
/
O
H
)
ii
(
H
B
)
i
(
2
2
6
2
A
A
Q7. Write down the reduction products of RCN, RNO2 and RCHO byB2H6
Q8. Identifythe gas produced during catalytic decomposition ofC2H5OH byhotAl2O3, whichdecolorises
Br2 water.
Q9. Completethefollowing reactions:
(i) BCl3 + NH4Cl Cl
H
C
C
140
5
6
0

 
 [A] 

 
 4
NaBH [B]
(ii) BCl3 + LiAlH4  [C] + LiCl +AlCl3
(iii) BCl3 + H2 + Cfibre 
 
 C
18000
[D] + HCl
(iv) Na2B4O7 + NH4Cl heat
red

 [E] + B2O3 + NaCl + H2O
(v) BCl3 + (C2H5)4N+ Cl–

 
 3
CHCl [F]
(vi) B2O3 + CaF2 + H2SO4 
 [G] + [H] + [I]
(vii) Al2O3 + Co(NO3)2 
 [J] + [K]+ [M]
Q10. Starting fromboric acid how would you prepare?
(a) Boric anhydride (b) Borontrichloride (c) Borontrifluoride (d) Boronhydrides
(e) Ethylborate (f) Meta and tetraboric acids
Q11. Boron onheating at 7000C inair gives white indusible amorphous powder (A), whichis decomposed
when heated in a current ofsteamto give a white powder (B) and a gas (C). Gas (C) turns red litmus
blue and in aqueous solution gives yellow colour with Nesseler's reagent. Compound (B) on strong
heating gives (D).Amixture of(D) and carbon on heating incurrent of Cl2 gives a colourless fuming
liquid (E). (E) reacts with hydrogen to giev (F), which on strong heating produce a gas (G) and the
fuming liquid (E). (G) on heating with(C) at 2000C produced inorganic benzene (H). Give (A) to (H)
and explainthe different reactions.
Q12. Amineral(A)on fusionwith Na2CO3 givesa white ppt. (B) and a solutionwhichon concentration and
cooling gives crystalsof(C). Compound (B)onstrong heating gives acolourless gas (D) anda solid(E).
Onpassinggas (D) throughaqueoussolutionof(E) againcompound (B) is formed. COmpound (C) on
treatment with hot conc. HClfollowed byhydrolysis gives compound (F). COmpound (F) on strong
heating gives (H)whichonheating withchromic sulphate gives agreenbeadofchromicborate and SO3
gas. What are (A) to (H)?Explainthe reactions involved.

Q13. Describe acidic nature ofBoric acid.
Q14. Completethefollowing
(a) BCl3 + Hg arc
electric
pressure
Low



 
 (b) AlCl3 + H2O 
(c) B + conc. HNO3  (d) B2O3 + Hg(CN)2 

EXERCISE II (B)
Q1. Although aluminiumis above hydrogen in the electrochemical series yet it is stable in air and water.
Explain. [IIT 1994]
Q2. The hydroxidesofaluminiumand ironare insoluble inwater. However, NaOH is used to separate one
fromtheother. Explain. [IIT 1991]
Q3. Aluminiumsulphide gives a foulodourwhen it becomes damp. Write a balanced chemicalequation for
the reaction. [IIT, July 1997]
Q4. Compound XonreductionwithLiAlH4 givesa hydrideYcontaining21.72% hydrogenalongwithother
products. ThecompoundYreacts withair explosivelyresulting inborontrioxide. IdensityXandY.Give
balanced reactions involved inthe formation ofYand its reactionwithair. Draw the structure ofY
.
[IIT 2001]
Q5. Acertainsalt (X) gives thefollowing tests:
(i) Itsaqueous solutionis alkalineto litmus.
(ii) Onstronglyheating it swells to give galssymaterial.
(iii) When concentrated H2SO4 is added to a hot concentrated solutionof(X), white crystals ofa weak
acidseparate out. Identify(X) and writedownthe chemicalequationforreactionat steps (i),(ii)and (iii).
[Roorkee 1991]
Q6. AninorganicLewis acid (X) showsthe following reactions:
(i) It fumesinmoist air.
(ii) The intensityoffumes increases when a rod dipped in NH4OH is brought near it.
(iii)An acidic solution of(X) on addition ofNH4Cland NH4OH gives a precipitate whichdissolves in
NaOH solution.
(iv)Anacidicsolutionof(X) doesnot giveprecipitate withH2S. Identify(X)and givechemicalequations
for reactions at steps (i) to (iii). [Roorkee 1994]
Q7. (i)Awhite precipitate(B) is formed when a mineral(A) is boiled with Na2CO3 solution.
(ii) Theprecipitate is filetered andthefilteratecontains two compounds(C) and (D). The compound(C)
is removed bycrystallisationand whenCO2 ispassed throughthe motherliquor left (D) changes to (C).
(iii) The compound (X) onstrongheating gives two compounds(D) and (E).
(iv) (E) on heating withcobalt oxide produces blue coloured substance (F).
Identify(A) to (F) and gives chemicalequations for the reactions at steps (i)to (iv). [Roorkee 1995]
Q8. Write the balanced equationfor the reaction ofAl4C3 and BF3 with water. [IIT 2002]
Q9. Write the chemicalreaction associated withthe 'borax bead test' ofcobalt (ii) oxide. [IIT 2000]
Q10. How is boronobtainedfromborax. Givechemicalequationswithreactionconditions.Write thestructure
ofB2H6 and itsreaction with HCl. [IIT 2002]
Q11. IdentifyAand B inthefollowing reactions:
Colemanite + (A)  Na2B4O7
Na2B4O7 + (B)  H3BO3 [IIT 1989]

Q12. AlF3 is not soluble in anhydrous HF but soluble in KF.
(a) Explainthe observation
(b) When BF3 is added to above solution.AlF3 is precipitated. Write balanced chemicalequation.
[IIT 2004]
Q13. Starting fromboric acid how would you prepare?
(a) Boric anhydride (b) Boric trichloride (c) Borontrifluoride (d) Boronhydrides
(e) Ethylborate (f) Meta and tetraboric acids
Q14. Explainthefollowing:
(i) Boronand aluminiumhalides behave as Lewis acids. [Roorkee 1985]
(ii) Borontribromide is stronger acidthan borontrifluoride. [Roorkee 1988]
(iii)Aluminiumforms [AlF6]3– ionbut borondoes not form[BF6]3– ion.
(iv) Boronhas highmelting andboiling points.
(v) The p-p back bonding occurs in the halide ofboron and not inthose ofaluminium.
Q15. Explainthefollowingwithappropriate reason:
(i)Althoughaluminiumis above hydrogeninthe electrochemicalseries, it is stable inair and water.
[IIT 1994]
(ii) Intheelectrolytic manufacture ofaluminium, carbonanodes are consumed.
(iii) Cryoliteis added to aluminainthe electrolytic manufactureofaluminium. [MLNR1988]
(iv)AnhydrousAlCl3 fumes inair. [Roorkee 1986]
(v)Alumis used insettling muddywater. [Roorkee 1985]
ANSWER KEY
EXERCISE I (A)
Q1. A Q2. A Q3. D Q4. A
Q5. D Q6. C Q7. C Q8. D
Q9. D Q10. D Q11. D Q12. A
Q13. B Q14. C Q15. C Q16. A
Q17. A
EXERCISE I (B)
Q1. B Q2. A Q3. C Q4. D
Q5. B Q6. D Q7. A Q8. B
Q9. B